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T O P I C R E V I E W

Paul78zephyr

I've read about the lightning strikes on Apollo 12 during launch. The whole "just lost the platform gang" and "SCE to Aux" is well documented.

But the command module lost its guidance platform and the Saturn V did not. Why?

Did the the tripping (going off line) of the fuel cells/AC busses cause the CM platform to be lost or could the platform have been lost even if the fuel cells had stayed online? Wasn't the guidance platform's power supply backed up by the CMs batteries?

Finally if the Saturn's guidance had been lost could Conrad have manually flown the big Saturn to orbit? Did they train for that?

If they had to abort at (or about) the point that Aaron called for SCE to Aux what would the abort mode have been? One Bravo?

Obviousman

The lightning strike on the spacecraft caused a surge which knocked a number of systems offline — one of these being the CM guidance platform. Two of the three CM re-entry batteries took over the load for a number of systems, but the platform had tumbled.

Fortunately, engineers like redundancy and so a separate 'backup' guidance platform within the Instrument Unit interstage could continue to guide the spacecraft until they were in orbit and could realign the platform.

Without the IU platform, the Saturn would have probably tumbled out of control. The crew would not have been able to fly 'seat of the pants' out of it. If they reacted fast enough for an abort, I think it would have been a 1B or perhaps a 1C. I'm reasonably sure they had called Mode Bravo after the lightning strike, but I'm not sure when the Mode Charlie call came. I'm sure someone will clarify this.

Naraht

quote:Originally posted by Paul78zephyr:If they had to abort at (or about) the point that Aaron called for 'SCE to Aux' what would the abort mode have been? One Bravo?

According to the transcript, the "One Bravo" call came at 43 seconds. Conrad reported losing the platform at 1:02. The first "SCE to Aux" instruction was sent to the crew at 1:36, and the "One Charlie" call came at 1:58. So definitely One Bravo.

Presumably if the call had been abort rather than "SCE to Aux" it would have been passed up to the crew even faster, because that was a contingency they had trained for, and time was of the essence.

I don't think there was any chance of flying a Saturn V manually; certainly I've never heard of anyone training for it. Gerry Griffin said that he very much expected John Aaron to recommend an abort,

quote:Fortunately, engineers like redundancy and so a separate "backup" guidance platform within the Instrument Unit interstage could continue to guide the spacecraft until they were in orbit and could realign the platform.

Are you saying the Saturn's IU HAD been affected and had switched to a backup mode? That I've never heard of... and I do not think that is correct.

My understanding is that the Saturn and the spacecraft (CSM) each had its own guidance systems. Completely saperate units. But the CSMs guidance failed and the Saturn's (IU) did not. Why?

Naraht

According to a footnote in Murray and Cox's "Apollo" (fount of all wisdom):

Part of the reason the spacecraft was so affected by the lightning while the Saturn was not involved the spacecraft's greater exposure — it was positioned like the tip of a lightning rod — and part of it was luck, as [Don] Arabian emphatically pointed out... In the case of the IU, induced currents reached the guidance system's circuits but the computer software kept the platform from tumbling.

Naraht

If you want more technical info than that, you'll want to look at the Apollo 12 mission report and at NASA's "Analysis of Apollo 12 Lightning Incident" (94 pages long), both of which are available in several places online.

MCroft04

quote:Originally posted by Naraht:I don't think there was any chance of flying a Saturn V manually; certainly I've never heard of anyone training for it.

In "Two Sides of the Moon", Dave Scott writes on page 283; "the Saturn V could be flown using the spacecraft's guidance system. This could be effected by computer or else I could use the joystick-rotational hand controller-in my right hand to steer the Saturn V with its three separate stages. In the latter case, manual control was activated by turning the T-handle in my left hand in a clockwise direction 45 degrees. The Saturn would immediately respond to signals from the Command Module."

I don't know if Apollo 12 had the same capability.

Paul78zephyr

I could have sworn that I read somewhere that Conrad had said that he would have not have aborted and would have flown the Saturn into orbit (or tried to) no matter what. Ill try to look for that.

Obviousman

In the Apollo 12 technical debrief, Conrad says:

I never considered any kind of an abort. The only concern that passed my mind was winding up in orbit with a dead spacecraft. As far as I could see, as long as Al said we had power on the buses and the COMM was good, we'd press on.

Obviousman

Yes, you are right. I thought primary guidance came from the CM but primary guidance for the Saturn actually came from the IU.

Obviousman

According to a Powerpoint guide on the Saturn V, the AGC program 11 (which monitored the boost phase) had the ability to guide the Saturn.

taneal1

quote:Originally posted by MCroft04:"I don't think there was any chance of flying a Saturn V manually; certainly I've never heard of anyone training for it."

Neil Armstrong mentioned that this "manual" capability had existed since Apollo 10. He himself had done quite a bit of work on the feasibility of manually flying a booster into oribit for the X-20 program.

Blackarrow

After Apollo 11 I was absolutely captivated by anything and everything to do with Apollo. As Nov. 14th approached I got more and more excited. The days passed very slowly, and on the launch day itself time seemed to slow to a crawl. (November 13th was my 15th birthday: I have absolutely no memory of that day. It was completely overshadowed by what was about to happen thousands of miles away). School on launch day was interminable.

At long last, I got home and endured the next hour until BBC TV live coverage began around 5.00pm. I was disappointed to learn that the weather was cloudy with rain at KSC but I don't recall any serious suggestion that the launch might be delayed. Saturn V launches always took place on time! But I realised there would only be a brief view of the rocket.

When the countdown reached zero and I heard "We have a lift-off!" I was elated. I saw the Saturn lift off and disappear into the clouds, and I heard Pete Conrad chattering away like a kid going on a picnic. I then remember a lot of excited communications between Apollo and Houston and I had a vague impression that things weren't going entirely according to plan, but I never sensed a real danger to the spacecraft or the crew, and certainly never felt that there might be an abort.

At some point I heard there had been a lightning strike, but again it didn't dawn on me that the mission might be in jeopardy. By the time Apollo 12 entered orbit the immediate crisis was over, but listening to the launch from ground to orbit I never knew there were any real concerns.

Okay, I had just turned 15. I wasn't aware of exactly what was going on, but if you weren't around at the time, you probably can't understand how much faith people put in Apollo's technology. I never doubted that Armstrong and Aldrin would land safely, and I never doubted that Pete Conrad would overcome any minor electrical problems. It wasn't until Apollo 13 that it finally dawned on me that astronauts might actually die in space.

For those of you whose memories of space exploration are dominated by Challenger and Columbia, it may be hard to understand just how much faith people put in the Apollo missions being successful and the astronauts returning safely.

capcom9

Filling in some details to what Naraht quoted from Murray and Cox's "Apollo"...

The reason Apollo 12 was able to get into orbit was that the guidance system for the Saturn V, buried within the IU at the top of the S-IVB stage, was unafftected by the lightning. If its platform had tumbled, the Saturn would have gone out of control within a few seconds. Part of the reason the spacecraft was so affected by the lightning while the Saturn was not involved the spacecraft's greater exposure - it was positioned like a lightning rod - and part of it was luck, as Arabian emphatically pointed out. Neither the spacecraft nor the launch vehicle had been designed with lightning in mind. In the case of the IU, induced currents reached the guidance system's circuits but the computer software kept the platform from tumbling. In addition, the incident on Apollo 12 dramatically vindicated the decision early in the 1960's to have separate guidance systems for the spacecraft and the launch vehicle.

While working the problem, Gerry Griffin recalled that Chris Kraft attempted to take some of the pressure off him by saying "Don't forget that we don't HAVE to go to the moon today."

Paul78zephyr

When exactly (T+?) was the Apollo 12 Saturn V hit by lightning. Would the outcome have been any different if the lightning had struck just before launch (i.e. between T-20 and T-0)? What if it had hit 5, 10 or 20 seconds after it actually did?

Also, by not aborting did Conrad break (or bend) any of the abort rules they had written?

Editor's note: Threads merged.

328KF

I did alot of research on Apollo 12 as co-author of the upcoming book Footprints in the Dust. The Saturn V was hit twice at T+36.5 seconds and at T+52 seconds.

There were no simulations or rules to fall back on in this case. While it was immediately apparent to the crew that something had gone terribly wrong with the electrical system, co-incident with a brief white flash observed only by Conrad, the ground had no idea what had happened and no data to help sort it out.

There was no active lightning in the area prior to launch. The ionized exhaust of the rocket itself created the conditions which led to the discharge. While very unlikely, had it happened prior to launch my assumption is that the count would have been stopped.

Did Conrad "break" any rules? No. there were no rules governing lightning strikes in flight. He had a flying rocket going on the right direction, so he did exactly the right thing...nothing. He let Bean and Gordon work out the electrical issues with the spacecraft and the rest is history.

NASAROB

I recall reading somewhere that once Apollo 12 reached orbit they tested all the crafts systems. They only thing they could not verify were the pyros that deploy the parachutes. They decided to go on with the mission because if they did not work now they still wouldn't work at the end of the mission.

Editor's note: Threads merged.

LM-12

Those watching the launch from the Vehicle Assembly Building (VAB) viewing site saw Apollo 12 disappear into the overcast clouds shortly after the vehicle cleared the tower.

This launch footage from British Pathe was taken further south and shows the vehicle later in the ascent. Apollo 12 cleared the tower at T+00:12 seconds, and CMP Richard Gordon said "What the hell was that?" at T+00:37 seconds.

Does the launch footage end before or after T+00:37 seconds?

p51

quote:Originally posted by Paul78zephyr:Conrad had said that he would have not have aborted...

I personally heard Conrad tell someone that at an event in the 80s. He was asked if he'd ever thought of aborting. I don't remember the words, but it was something like, "I'd have flown it as long as I could have," which I took to mean up to the point it stopped being a flyable machine (like the old pilot's adage of flying as far into the crash as possible).

SkyMan1958

Here are the first two launch checklist pages to give you an idea of what was supposed to happen when. Needless to say, things happened far to fast for the astronauts to actually write anything in the checklist pages. One would assume there were comparable cue cards somewhere on the instrument panel in front of the astronauts.

Here are a couple of pix of the event as signed by Bean and Gordon...

LM-12

You can see the Cape Lighthouse in the foreground of the film.

The post-flight analysis of the lightning incident mentions altitudes: at 36.5 seconds the vehicle was at about 6400 feet, and at 52 seconds the vehicle was at about 14,400 feet.